The present invention relates to the preparation and utilization of monolayer particulate films and, more specifically, to the utilization of monolayer films in applications such as semiconductor fabrication, photoresist processing, dielectric layering, integrated optical device fabrication, polymer science, adhesive technology, etc.
Particulate films that are on the order of one molecule or one particle thick are commonly referred to as ultrathin films, monomolecular layers, or monolayer films. Monolayer films are commonly produced from amphiphilic low molecular weight molecules, i.e., molecules that include a polar end and a non-polar or hydrophobic end. Disposed on the surface of a non-solvent, such as water, the polar ends of the molecules or particles will tend towards the water, while the nonpolar or hydrophobic ends will tend to project into the gas space above. Typically, small amounts of such amphiphilic substances are dissolved in a suitable solvent and, for example, introduced onto a water surface of sufficient size. The solution spreads across the surface of the water and, with evaporation of the solvent, the molecules form an initially noncohesive, monomolecular layer. By moving a suitable barrier, the water surface is reduced in size in a dimension along the surface of the water and the non-cohesive layer is compressed into a cohesive, monomolecular layer exhibiting order at the molecular level. When this quasi-solid state of this monomolecular layer is reached, further movement of this barrier meets with a clearly measurable resistance, which indicates that the cohesive state has been reached. Suitable substrates can then be immersed through the monomolecular layer into the water and in turn become coated with a cohesive monomolecular layer of the amphiphilic substance. The stated process can be repeated. This coating technique is known to those skilled in the art as the Langmuir-Blodgett technique.
Ultra-thin films prepared and applied using conventional Langmuir-Blodgett techniques are not however completely free from voids between the molecules or particles of the film. As a result, the ultra-thin films prepared according to the conventional Langmuir-Blodgett techniques may be unsuitable for specific thin film applications, particularly those related to the fabrication of semiconductor devices. Accordingly, the present inventor has recognized a need for an improved technique for preparing and utilizing cohesive monolayer films.